An FES therapy uses a low-frequency current to stimulate denervated muscles, making muscle contraction in order to replace or correct functions that organs and limbs have lost. At present, research and application on FES have been involved in various fields of clinical treatment. In general, an FES device is a portable stimulator with two or four channels.
The FES can assist users with upper motor neuron injury to complete some functional activities, such as walking, grasping, and coordinated movement, which can accelerate recovery of voluntary control. Upper motor neuron injury includes cerebrovascular disease, brain trauma, spinal cord injury, cerebral palsy, etc. Limb movement is critical to the rehabilitation of these users, especially the users with spinal cord injury. The latest study found that the electrical signal, generated by the limb movement, can cause irritation on the spinal cord stump, which achieves the restoration of part of the spinal cord continuity. Some scientists have proposed a FES-assisted pedalling training method, which can restore muscle strength and promote local tissue repair of spinal cord injury.
As an important part of the FES system, a boost module provides high voltage for a stimulation output channel. Especially, when the electrical stimulation is used to generate limb movements, the boost module is required to provide higher and more stable voltage compared with the case of using the electrical stimulation for easing pain. However, output strength and load capacity of commercial electrical stimulation devices are relatively low at present. They cannot be used for the stimulation requirement of large load (for example, the electrical stimulation assists users to complete a treadmill exercise). Moreover, the security and reliability are also low. In particular, when a user uses a household electrical stimulation device without professional guidance and monitoring, the user may induces abnormal heartbeat and muscle spasm abruptly owing to electrical stimulation. It will cause secondary damage if the electrical stimulation cannot be disconnected instantly.
Thus, disadvantages of a conventional FES system may consist in:                1. The boost module cannot provide the higher and more stable electrical stimulation because of its limited boost capacity and low stimulation intensity; and        2. There is a security risk in the case of high-voltage stimulation. That is, the security and reliability are low.        